The present invention relates generally to communications between communication stations of a radio communication system, such as a WLAN (Wireless Local Area Network) operable generally pursuant to the IEEE 802.11 standard. More particularly, the present invention relates to an assembly, and an associated method, by which to facilitate allocation of frequencies upon which to communicate data during operation of the communication system. Signal messages are generated and communicated between the communication stations to facilitate allocation of frequencies in a manner to attain a selected statistical spread of electromagnetic energy across a range of frequencies.
Advancements in communication technologies have permitted the introduction, and popularization, of new types of communication systems. In various of such new types of communication systems, the rate of data transmission and the corresponding amount of data permitted to be communicated, has increased relative to existing types of communication systems.
New types of radio communication systems are exemplary of communication systems made possible as a result of advancements in communication technologies. Communication channels of a radio communication system are formed upon radio-links, thereby obviating the need for conventional wireline connections between sending and receiving stations operable therein. A radio communication system, therefore, inherently permits increased communication mobility in contrast to conventional wireline systems.
Bandwidth limitations sometimes limit the communication capacity of the communication system. That is to say, the bandwidth capacity of the communication channel, or channels, available to a communication system to communicate information between sending and receiving stations is sometimes limited. And, the limited capacity of the communication channel, or channels, limits increase of the communication capacity of the communication system. The communication capacity of the radio communication system is particularly susceptible to capacity limitation resulting from communication channel bandwidth limitations. Generally, a radio communication system is allocated a limited portion of the electromagnetic spectrum upon which to define communication channels. Communication capacity increase of a radio communication system is, therefore, sometimes limited by such allocation. Increase of the communication capacity of the radio communication system, therefore, is sometimes only possible if the efficiency by which the allocated spectrum is used is increased.
Digital communication techniques provide a manner by which the bandwidth efficiency of communications in the communication system may be increased. Because of the particular need in a radio communication system to efficiently utilize the spectrum allocated in such a system, the use of digital communication techniques is particularly advantageously implemented therein.
When digital communication techniques are used, information which is to be communicated is digitized. In one technique, the digitized information is formatted into packets, and the packets are communicated to effectuate the communication. Individual ones, or groups, of the packets of data can be communicated at discrete intervals, and, once communicated, concatenated together to recreate the informational content contained therein.
Because packets of data can be communicated at the discrete intervals, a communication channel need not be dedicated solely for the communication of packet data generated by one sending station to one receiving station as conventionally required in circuit-switched communications. Instead, a single channel can be shared amongst a plurality of different sending and receiving station-pairs. Because a single channel can be utilized to effectuate communications by the plurality of pairs of communication stations, improved communication capacity is possible.
Packet data communications are effectuated, for instance, in conventional LANs (Local Area Networks). Wireless networks, operable in manners analogous to wired LANs, have also been developed and are utilized to communicate packets of data over a radio-link, thereby to effectuate communications between a sending and a receiving station.
For example, an IEEE (Institute of Electrical and Electronic Engineers) 802.11 standard defines a system for operation of a wireless LAN. Three physical layers are defined in the 802.11, the 802.11a, and the 802.11b standards. The physical layers defined in the 802.11a standard already exist and form the 5 GHz 802.11 standard.
Proposals have been set forth to utilize an unlicensed band located at 5 GHz, also to implement a WLAN operable generally pursuant to the IEEE 802.11 standard. While 5 GHz band is unlicensed, at least in Europe, compliance with certain regulations must be met when communicating in the 5 GHz band. Such regulations include adherence to allowable electromagnetic emissions. A communication system operable at the 5 GHz band must be capable of dynamic adaptation to local interference conditions. Also, systems operable at the 5 GHz band must generate electromagnetic energy emissions which are spread over available frequency channels defined therein. The requirement is a statistical requirement that must be satisfied on a large scale rather than that of a single system. For instance, in systems operable in the 5,470-5,725 MHz range, electromagnetic emissions must be spread across a minimum of 255 MHz.
The IEEE 802.11 standard does not provide for dynamic frequency selection which would facilitate compliance with the electromagnetic emissions spreading regulations.
If a manner could be provided by which to adapt the IEEE 802.11 standard to facilitate frequency allocation upon which to communicate data during operation of a communication system to achieve emission spreading, a communication system operable pursuant to such standard could be used in the 5 GHz frequency band.
It is in light of this background information related to the communication of data in a radio communication system that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides an assembly, and an associated method, by which to facilitate allocation of frequency channels in a radio communication system, such as a WLAN (Wireless Local Area Network) operable generally pursuant to the IEEE 802.11 standard.
Operation of an embodiment of the present invention provides a manner by which to facilitate frequency allocations of frequencies upon which to communicate data during operation of the communication system. Through appropriate frequency allocations, a selected statistical spread of electromagnetic energy, generated as a product of operation of the communication system, across a range of frequencies is achieved.
In one aspect of the present invention, a message is generated during operation of the radio communication system. The message is of a value to indicate that a change of frequency upon which to communicate subsequent data shall be changed. Such a message is broadcast at selected intervals. A mobile station operable in the communication system is turned-on, such as by exiting of the mobile station out of a sleep mode, and is able to detect the message broadcast at the selected intervals.
In another aspect of the present invention, a message is generated at the network infrastructure of the radio communication system. The message is of a value to indicate the frequency channel upon which to communicate subsequent data. In one message, a single frequency channel is indicated. In another message, more than one frequency channels are indicated from which subsequent selection is made.
In another aspect of the present invention, a message is generated at the network infrastructure of the radio communication system. The message is of a value to indicate, at least on a relative basis, when a change in frequency channel allocation shall be made. When detected by a mobile station, the mobile station is thereby able to determine when to become tuned to the newly-allocated frequency channel. The relative time is comprised of, for instance, a count of a number of beacons prior to which the frequency allocation change shall be effectuated.
In another aspect of the present invention, a message is generated at a mobile station operable in the radio communication system. The message is generated responsive to a prior message generated by the network infrastructure associated with a change in frequency allocation of a frequency channel upon which to communicate subsequent data. The message is of a value to select one of a first and at least a second frequency channel upon which to communicate the subsequent data.
In another aspect of the present invention, a message is generated at the mobile station of the radio communication system. The message is generated responsive to prior receipt of a message generated by the network infrastructure and communicated to the mobile station. The message is of a value to indicate whether the frequency channel upon which communication of data is subsequently to be made.
In another aspect of the present invention, a determination is made at the mobile station of the availability of newly-allocated frequency channels allocated to the mobile station for subsequent communication of data. If the frequency channel is determined to be available for the subsequent communications, an indication of the availability is returned to the network infrastructure. If a determination is made that the frequency channel or frequency channels are not available for subsequent communications, a corresponding indication is similarly returned to the network infrastructure.
In another aspect of the present invention, messages are generated by a mobile station which forms an IBSS (independent BSS) in an infrastructureless system. Messages representative of a change of frequency upon which to communicate subsequent data and of the selected frequency channel are transmitted by the IBSS.
In one implementation, a WLAN (Wireless Local Area Network) system constructed generally pursuant to the IEEE 802.11 standard is installed and operable at the 5 GHz band. Frequency channel allocations are made in manners to attain a selected statistical spread of electromagnetic energy across a range of frequencies. Messages are generated at both the network infrastructure and at a mobile station operable in the WLAN system. Network-generated messages are transmitted to the mobile station to inform the mobile station of a change in frequency channel allocation as well as indications of at when the frequency allocation changes shall be effectuated. Messages generated by the mobile station indicate whether a frequency channel is available upon which to communicate data as well as to acknowledge acceptance of an allocated frequency channel.
In these and other aspects, therefore, an assembly, and an associated method, is provided for facilitating dynamic selection of frequency allocations upon which to communicate data in a radio communication system. The radio communication system is operable to communicate data between a mobile station and a fixed-site communication station. The fixed-site communication station forms a portion of network infrastructure of the communication system. At least a first dynamic frequency selection message generator is coupled to at least one of the network infrastructure and the mobile station. The at least first dynamic frequency selection message generator generates a dynamic frequency selection message. The dynamic frequency selection message is of values indicative of an indicia associated with a frequency allocation by which to communicate subsequent data. The frequency allocation is made to attain a statistical spreading of electromagnetic energy over a selected frequency range.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention, and the appended claims.